The present invention relates to a vial, particularly a glass vial, wherein the plane along the narrowest part of the neck portion of the vial obliquely crosses at a given angle with respect to the axial line of the vial thereby decreasing the production of broken glass pieces which tend to fall into the vial during the cutting operation of the branch pipe portion from the main body of the vial.
In a glass vial such as that used for hypodermic purposes in medical applications, it is known that the cutting operation of the vial branch pipe portion causes the glass to be broken to pieces, whereby some of the broken pieces drop into the vial body thereby polluting the contents thereof. It is almost impossible, under the existing circumstances, to completely prevent the glass from being broken into pieces. Some attempts have been already performed to prevent, to a certain degree, the glass from being broken into pieces or to decrease the broken glass pieces to some extent. For example, a positive pressure condition has been produced within the vial by some means; a scratch for cutting operation is provided in advance at one point of the vial neck portion (one-point-cut vial); a tackifier material is applied upon the inner face and/or the outer face of the vial neck portion; one or more swellings are formed in the branch pipe portion of the vial; the cutting position of the vial is varied; a special vial cutter is used; and so on.
However, these known methods required special incidental facilities to employ such methods. The molding operation of the vial is difficult to perform or the results were not sufficient. According to the experiments conducted on the above-described one-point-cut vial (2 ml in capacity) by the present inventors, the degree of glass was recorded as shown in Table 1.
TABLE 1 ______________________________________ Vials 2 ml One-Point-Cut Size Of Broken Pieces Experiments No. 10.about.24.mu. 25.about.49.mu. 50.mu..about. ______________________________________ 1 2 1 0 2 0 0 0 3 5 1 0 4 3 2 1 5 1 0 0 6 3 0 0 7 1 0 1 8 2 0 0 9 2 1 0 10 0 1 0 11 3 0 1 12 2 1 0 13 0 0 0 14 11 1 3 15 2 0 2 16 9 5 0 17 3 1 0 18 5 1 1 19 10 2 0 20 1 1 0 --X 3.25 0.9 0.45 Total --X 4.6 ______________________________________
After the detailed observation of the broken glass pieces caused during the cutting operation of the vial, the present inventors have found out that more broken glass pieces are produced on the compression side of the vial to be cut, instead of the on the tensile side thereof. Namely, when the branch pipe portion 2 of the vial is depressed as shown in FIG. 1 from one side to the other side along the direction of a dotted-line arrow, and is cut from the vial body 1 at the narrowest part 3 of the neck portion along the one-dot chain line A-B, more broken glass pieces are caused on the compression side A than the tensile side B. This fact indicates that innumerable break lines are caused, thus resulting in roughness in the cut face (FIG. 3) on the compression side as compared with the cut face (FIG. 4) on the tensile side as shown in FIG. 3 and FIG. 4, each showing an enlarged plane view of the cut face of the respective sides. Namely, the cut face on the tensile side B of the neck portion 3 shown in FIG. 4 indicates filed scratches 4 only, which are normally provided on the narrowest portion 3 of the vial, and also indicates relatively clear breaks. Fine, irregular break lines 5 and distorted lines 6 are produced across a considerably wide portion of the cut face, as shown in FIG. 3, on the cut face of the compression side A of the vial, thus indicating many broken glass pieces produced during the cutting operation of the vial. Therefore, it can be easily imagined that the broken glass pieces can be prevented, to a certain degree, by utilizing a cutting method which causes the stress, produced during the cutting operation of the vial branch pipe portion, to function as tensile stress with respect to the neck portion of the vial. However, both end portions cannot be cut along the axial line of the vial by the mutual pulling operations of the end portions. The present inventors have developed a vial, after examining the shape of the neck portion, wherein the stress produced during cutting may be operated in the pulling direction as much as possible. Namely, the present invention relates to a glass vial, wherein the plane along the narrowest part of the neck portion of the vial whose branch pipe portion is to be cut obliquely crosses at a given angle with respect to the axial line of the vial.